Kaolin clays for pitch control

ABSTRACT

Kaolin clay treated with 0.5 to 1.5 wt. % of aluminum chlorohydrate or a double hydroxide of aluminum and magnesium are an effective pitch adsorption agent for use in paper making processes.

FIELD OF THE INVENTION

This invention relates to the control of pitch deposition in papermaking operations, and more particularly relates to the use of modifiedkaolin clays for control of pitch deposition in paper making operations.

BACKGROUND OF THE INVENTION

In the operation of a pulp mill in the production of paper, one of therecurring problems is control of the pitch which is deposited during theoperation. Pitch is the sticky, resinous substance of varyingcomposition which originates from the extractive fraction of wood in thepaper making process. Pitch is reported to be composed of fatty acidsand rosin acids and their corresponding calcium, magnesium, and sodiumsalts. The pitch exists in its dispersed state until chemical changes inthe paper furnish cause it to agglomerate and deposit on screens, feltsor other paper machine surfaces. This results in holes or breaks in thesheet and expensive down time for clean ups. It is reported that thepaper industry loses 30 million dollars annually because of lostproduction caused by pitch problems. Though various measures have beentaken to combat these problems, by far the most effective measure takento the present date is the use of talc to adsorb the pitch, therebypreventing agglomeration and subsequent deposition. The talc pitchcomplex is carried out as part of the final product so that no problemarises from its presence. There is discussion of this problem by Gill in"Pulp Processing", Vol. 48, No. 9 (August, 1974) p. 104. In addition,there is disclosed in Tappi Conference Paper: Alkaline Pulping Test 1976a publication by Albert R. Kaiser of St. Regis Paper Company on "The Useof Talc to Control Pitch Deposition", pps. 133-134.

Use of talc as a pitch deposition control agent, however, is expensivebecause of the price of talc, so there is a need to increase efficiencyof such pitch deposition controls, while at the same time increasingcost savings in operation of the process.

SUMMARY OF THE INVENTION

It is accordingly one object of the present invention to provide amethod for the control of pitch which is deposited in paper makingprocesses.

A further object of the invention is to provide a modified kaolin clayfor use in the control of pitch in paper making systems.

A still further object of the invention is to provide a modified kaolinclay which has been treated with aluminum chlorohydrate or hydrotalcite(or hydrotalcite analogues which are magnesium-aluminum doublehydroxides of varying [Al]/[Al]+[Mg] molar ratios), which modifiedkaolin clay is useful in the control of pitch in a paper making process.

Other objects and advantages of the present invention will becomeapparent as the description thereof proceeds.

In satisfaction of the foregoing objects and advantages, there isprovided by this invention a kaolin clay which has been treated withaluminum chlorohydrate or hydrotalcite or analogue, either in the dryform or slurry form, said treated kaolin clay being useful for thecontrol of pitch deposition in a paper making process.

There is also provide by the present invention a method for theadsorption of pitch and thus the control of pitch deposition in a papermaking process which comprises addition of an aluminumchlorohydrate-treated kaolin clay or a hydrotalcite-treated kaolin clayto the paper furnish.

BRIEF DESCRIPTION OF THE DRAWING

Reference is now made to the drawing accompanying this applicationwherein the FIGURE is a graph showing a comparison of different claysand their treatment levels of aluminum chlorohydrate with respect to theamount of pitch adsorbed.

DESCRIPTION OF PREFERRED EMBODIMENTS

As indicated above, this invention is concerned with modification ofkaolin clay and use of the modified kaolin clay as a pitch control agentin the paper making industry. According to this invention it has beenunexpectedly discovered that kaolin clays can be chemically modified toimprove their pitch adsorption characteristics so that they can serve asreplacements for talc in the paper making industry and provide increasedefficiency and cost savings.

In accordance with this invention it has been discovered that a kaolinclay which has been modified by treatment with aluminum chlorohydrate ora hydrotalcite will provide normally inert kaolin clay with qualitieswhich enables the resulting modified clay to have pitch adsorptioncharacteristics which makes the modified clay eminently suitable as apitch adsorption agent in paper making processes.

Kaolin clays are well known materials and various kaolin clays are minedthroughout the southeast and are identified, for example, by the regionfrom which they are obtained, such as middle Georgia clays and eastGeorgia clays. All such clays are considered to be useful within thescope of the present invention.

The kaolin clay according to the present invention is modified bytreatment with either aluminum chlorohydrate or hydrotalcite. Aluminumchlorohydrate is a known material and is also referred to as an aluminumchlorohydroxide complex. It is of the formula Al₂ (OH)₅ Cl·2H₂ O.Aluminum chlorohydrate is sold commercially under the name Chlorhydrol®by Reheis Chemical. As available commercially, Chlorhydrol® is a clear,colorless 50% solution and is preferably used in that form in thisinvention. However, other physical forms of the aluminum chlorohydratemay also be used in treatment of the clay.

In the present invention the clay may be treated in dry form with thealuminum chlorohydrate or it may be treated as a slurry. It is highlypreferred that the modified clay be prepared in slurry form, since testresults have shown that the slurry treatment process is a more simpleprocedure and the nature of slurry treatment lends itself to moreuniform mixtures. Thus, this represents the preferred procedure.

It has been discovered that both fine particle size (90-99% finer than2μ), high surface area (22 m² /gm) clays and coarse particle size (80%finer than 2μ or lower), low surface area clays (12 m² /gm or less)respond equally well to treatment with aluminum chlorohydrate to produceeffective pitch control agents. Further, it has been found thatdegritted crude clays as well as fractionated and leached beneficiatedclay fractions can be effectively treated with aluminum chlorohydrate toproduce pitch control products. It is preferred that crude clay orfractionated clay slurries contain a minimum amount of dispersant(preferably 0.1-0.15% of Calgon) prior to treatment with aluminumchlorohydrate, and that leached beneficiated clay fractions be treatedwith aluminum chlorohydrate as undispersed filter cake slurries.Further, the amount of aluminum chlorohydrate which should be used totreat the clay should range from about 0.5 to 1.5 wt. % and morepreferably from about 0.75 to 1.25 wt. %. It has been found that thisminimum amount of aluminum chlorohydrate is effective to modify the clayin such manner that the resulting modified clay excels as a pitchcontrol agent.

The treatment of the kaolin clay with the aluminum chlorohydrate ispreferably carried out by forming a clay slurry at a solids content ofabout 15 to 50 wt. %, preferably 30%. Thereafter, with agitation,sufficient aluminum chlorohydrate, such as a 30 to 60 wt. % solution,and preferably a 50 wt. % solution, is added to give a total treatmentlevel based on the clay weight of 0.5-1.5%, and preferably 0.75 to1.25%. The treated slurry is then blunged for about 5 to 60 minutes,preferably 10 to 20 minutes, and then is either spray dried or filteredand either dried as a cake or reslurried at 30% solids and spray dried.It has been found that the treated slurry may be stored for several daysprior to drying without affecting the pitch adsorption properties.

The modified clay may also be formed from a dry clay by treatment withaluminum chlorohydrate. In this procedure, the aluminum chlorohydratesuspension is added directly to dry clay to achieve uniform and thoroughmixing and a resultant moistened clay. The resultant treated clay iseither oven dried or dried using a rotary dryer/flash dryer combinationand milled to the desired fineness of grind.

While either slurry treatment or dry treatment of the clays may be used,use of the slurry process is preferred since it is a comparativelysimple process and the nature of slurry treatment lends itself to moreuniform mixing. Dry treatment of the clays requires a great deal ofmixing to ensure uniformity and proper distribution of the aluminumchlorohydrate and higher drying costs may be encountered. For thesereasons, the slurry treatment is preferred.

In a second embodiment of the present invention, the clay may be treatedwith a double hydroxide of magnesium and aluminum to modify the clay ina manner to make it useful as a pitch control agent. The recognizedmineral form of magnesium and aluminum double hydroxide is calledhydrotalcite and is of the formula Mg₆ Al₂ (OH₁₆ CO₃ ·4H₂ O. The termhydrotalcite will be used to refer to the recognized mineral form aswell as hydrotalcite analogues which are magnesium-aluminum doublehydroxides of varying molar ratios.

According to this invention it is preferred that the clay be treatedwith hydrotalcite-like materials which have been produced in-situ fromaluminum chloride and magnesium chloride. In this reaction, the in situformation of the hydrotalcite in a clay slurry is achieved by theaddition of desired quantities of 1.0M AlCl₃ and 1.0M MgCl₂ to a 10 to30 percent solids aqueous clay slurry, preferably 20% solids, andblunging to achieve good mixing. A time of about 5 to 15 minutes,preferably 10 minutes, is preferred. Thereafter, sodium hydroxide, suchas 2M aqueous sodium hydroxide solution, is slowly added to achieve a pHin the range of 10.0 to 11.0, preferably 10.5. The slurry is thenblunged for 5 to 15 minutes and filtered as on a Buchner funnel. Thefilter cake is then reslurried at 20 to 40 wt. % solids, refiltered anddried at 120° C., then hammer-milled to desired fineness of grind. Thetreatment level will depend on the ratio of aluminum and magnesium andthe percent alumina, as well as percent magnesium oxide per 100 parts ofclay. The following represents a sample calculation to achieve a propertreatment level for in situ formation of the hydrotalcite.

Sample Calculation of Treatment Level for in situ Formation ofHydrotalcite

Treatment Level: Al/Al+Mg=0.67 %Al₂ O₃ =0.68% %MgO=0.27%

ml 1.0M AlCl₃ added to 200 g clay=26.8

ml 1.0M MgCl₂ added to 200 g clay=13.3

26.8 ml 1.0M AlCl₃ =2.8 m mole AlCl₃ --13.4 m mole Al₂ O₃

13.4 mole Al₂ O₃ ×102 mg Al₂ O₃ /mmole=1.367 g

1.367 g Al₂ O₃ /200 g clay=0.68 g Al₂ O₃ /100 g clay

13.2 ml 1.0M MgCl₂ =13.2 m mole MgCl₂ --13.2 ml MgO

13.2 m mole MgO×40.3 mg MgO/m mole MgO=0.532 g

0.532 g MgO/200 g clay=0.267 g MgO/100 g clay ##EQU1##

It will be seen from this calculation that the clay is treated with anamount of hydrotalcite which can range from 0.5 to 2.0 wt. %.

The results of laboratory tests indicate that clay modified withaluminum chlorohydrate or hydrotalcite have pitch adsorption qualitiesequal to, and in most cases superior to, those of the more expensivetalc. Thus, an aluminum chlorohydrate-kaolin combination was found toadsorb up to 96.25% of the synthetic pitch in test systems, as comparedto a 35-45% adsorption by talc. The treated clay performedsatisfactorily in paper filler applications. Chemical modification ofthe clay slurry using the in situ formation of hydrotalcite was alsoshown to be effective in pitch adsorption. However, the aluminumchlorohydrate treatment is more preferred in this invention sincehydrotalcite modified clays appeared to provide less consistent resultsthan the aluminum chlorohydrate modification. Also, the hydrotalcitemodification involves a multistep process, which is less economic thanthe aluminum chlorohydrate.

In order to evaluate the modified clay as a pitch control agent, testprocedures were utilized to evaluate the pitch adsorptive capacity ofthe agents. This laboratory evaluation allowed direct measurement ofadsorbed pitch on the test samples. The adsorbed pitch was extractedfrom the modified clays and reacted to form a colored pitch complexwhose concentration could be measured spectrophotometrically. Theresults were reported as percent of total amount of pitch adsorbed andwere compared with the 45% adsorptive capacity exhibited by talc. Themethod of evaluation of the pitch adsorptive capacities of mineralpowders was a variation of a procedure outlined by D. A. Hughes in TappiConference Papers, Vol. 60, No. 7, p. 144-146 (1977), the disclosure ofwhich is incorporated herein by reference. This involves the mixing of aknown quantity of a synthetic pitch with a dilute mineral solution. Themineral and any adsorbed pitch is then separated by centrifugation. Theliquid fraction is discarded while the mineral powder is dried. Asolvent reagent is then added to the dry mineral to extract the adsorbedpitch which may be present. The pitch is then quantifiedcolormetrically. In general, the results indicated that Mistron vaportalc adsorbs about 40-45% of the synthetic pitch, untreated kaolin clayadsorbs less than 1%, and aluminum chlorohydrate-modified clay adsorbsup to 96.25%, so that the effectiveness of the aluminum chlorohydratetreated clay is clearly apparent. This is shown in the drawingaccompanying the application where HSP, HP, HG and Omnifil are asdefined in the examples.

The following examples are presented to illustrate the invention.However, it is not to be considered as limited thereto, as obviousvariations thereon will become apparent to those skilled in the art. Inthe examples and throughout the specification, parts are by weightunless otherwise indicated.

In the following examples, the clays to be treated are referred to bythe tradenames Hydrasperse®(HSP), Hydraprint®(HP), Hydragloss®(HG),Hydrafine®(HF), and Omnifil®. These terms are trademarks of the J. M.Huber Corporation for the types of clays utilized. The aluminumchlorohydrate used in the examples was a colorless 50% aqueous solutionobtained from Reheis Chemical under the trademark Chlorhydrol®.

In these examples the effectiveness of pitch control powders wasevaluated by permitting contact between specially prepared syntheticpitch and the pitch control powder in an aqueous system. The adsorbedpitch was extracted from the powder and quantified colorimetrically. Itis difficult to extract actual pitch from a problem area in a paper milland utilize that pitch for evaluation, so that synthetic pitch wasprepared from actual components of typical pitch. The experimentalprocedure of the pitch preparation and evaluation involved preparing asynthetic pitch sample by combining 0.65 grams of ground gum rosin and0.35 grams of tall oil in an Erlenmeyer flask. The oily mixture was thenstirred with a glass stirring rod while 1M potassium hydroxide was addeddropwise until saponification resulted. Denatured ethanol (250 ml) wasadded to dissolve the synthetic pitch. The resulting concentration ofthe pitch preparation is 4 mg/ml.

The pitch adsorption test procedure comprised slurrying 10 grams of thetest clay in a Waring blender with 400 ml distilled water for 10minutes. 35 ml of distilled water was first added to 50 ml glasscentrifuge tubes, followed by 1 ml of the synthetic pitch preparation,and lastly 10 ml of the clay slurry. The mixture was then stirred with astirring rod for 15 seconds and centrifuged for 20 minutes at 2500 rpm.The supernatant was then poured off and discarded and the tubecontaining the mineral powder and adsorbed pitch was dried overnight at60° C.

After drying, 10 ml of chloroform-acetic anhydride (1:1) reagent wasadded to the tube and stirred to release the adsorbed pitch from themineral powder. The mixture was then centrifuged for 20 minutes so thatthe clear reagent remained at the top of the tube. The clear reagent waspoured off into a small beaker and 10 drops of concentrated sulfuricacid added to effect a color change. After exactly four minutes, theliquid was measured on a spectrophotometer set at 400 nm and theabsorbance value was compared to absorbance values of known quantitiesof extracted pitch.

EXAMPLE 1

A fine particle size east Georgia crude clay having a particle size ofabout 90% finer than two microns was slurried as approximately 40%solids using 0.15% by weight sodium hexametaphosphate as the dispersant.The dispersed slurry was degritted on a 325 mesh screen and thedegritted slurry divided into eight equal samples. Chlorhydrol® wasadded to the samples at levels ranging from 0.8 to 1.4% by weight activeChlorhydrol® to weight of clay. The control sample contained noChlorhydrol®. Each treated sample was mixed for three minutes under lowshear using a dispersator equipped with a cowles type blade. The treatedsamples were dried on a teflon coated pan, milled, and evaluated forpitch adsorption characteristics using the modified Hughes method.Results of the tests are given in Table I.

                  TABLE I                                                         ______________________________________                                        Effect of Chlorhydrol ® on Pitch Adsorption of Treated                    East Georgia Degritted Clay                                                   Treatment Level  Percent Pitch                                                lbs/t Chlorhydrol ®                                                                        Adsorbed                                                     ______________________________________                                         0               10.0                                                         16               93.75                                                        18               96.25                                                        20               93.75                                                        22               92.50                                                        24               90.0                                                         26               88.75                                                        28               22.50                                                        Mistron Vapor Talc                                                                             45.0                                                         ______________________________________                                    

The results show maximum pitch adsorption at 0.9% Chlorhydrol® withvalues decreasing with higher and lower Chlorhydrol® levels. Incomparison the untreated clay sample showed 10.0% pitch adsorption whilea Mistron Vapor talc showed 45.0% adsorption.

EXAMPLE 2

An undispersed leached filter cake sample of a middle Georgia clayhaving a particle size of about 82-84% finer than 2 microns was obtainedfor treatment with Chlorhydrol®. An undispersed slurry was prepared fromthe filer cake at 30% solids by adding water to the filter cake whilemixing under moderate shear. The slurry was divided into eight equalportions and treated with Chlorhydrol® in the same manner as Example 1.

                  TABLE II                                                        ______________________________________                                        Effect of Chlorhydrol ® on Pitch Adsorption of Treated                    Hydrasperse ® Filter Cake                                                 Treatment Level Consistency of                                                                              Percent                                         lbs/t Chlorhydrol ®                                                                       Treated Slurry                                                                              Adsorbed                                        ______________________________________                                        16              Very thick    75                                              18              Thick         80                                              20              Slightly Thick                                                                              79                                              22              Slightly Fluid                                                                              35                                              24              Moderately Fluid                                                                            17.5                                            26              Fluid         <10                                             28              Quite Fluid   <10                                             ______________________________________                                    

Results of the test given in Table II show a maximum adsorption of atreatment level of 18 lbs./t decreasing drastically at levels above 20lbs./t. In comparison the untreated control had less than 10% pitchadsorption and Mistron Vapor had 45% pitch adsorption. The results wouldindicate that the coarser particle size middle Georgia clays are moresensitive to overtreatment than the fine particle east Georgia clays.

EXAMPLE 3

A degritted east Georgia clay slurry was prepared in the same mannerdescribed in Example 1. The slurry was divided in half and each halftreated with 1% Chlorhydrol®. One-half was mixed for about 15 minutesand spray dried. The second-half was filtered on bottle filters, placedin a forced air oven and dried. Both samples were evaluated for pitchabsorption by the modified Hughes method.

The results shown in Table III indicate that some Chlorhydrol® was lostduring the filtration but that the resulting pitch adsorption of thetreated clay was still substantially higher than the value for talcwhile lower than the value for the unfiltered sample.

EXAMPLE 4

An unbeneficiated Hydrasperse® slurry prepared from middle Georgia crudeclay and having a particle size of about 84% minus two microns wasobtained and treated in the same manner as described in Example 3. Pitchadsorption characteristics as determined by the Modified Hughes methodis given in Table III.

                  TABLE III                                                       ______________________________________                                        Effect of Filtering Treated Slurry on Pitch Adsorption                        of East Georgia Clay                                                                         Percent Pitch Adsorbed                                                          Spray Dried,                                                                             Filtered                                          Example          As Is      Oven Dried                                        ______________________________________                                        Omnifil ® (Example 3)                                                                      82.5       73.0                                              Hydrasperse ® (Example 4)                                                                  66.0       47.5                                              Georgia                                                                       ______________________________________                                    

The filtered middle Georgia sample had a pitch adsorption valuesignificantly lower than the unfiltered control indicating a substantialloss of treating chemical. The pitch adsorption value was stillequivalent to talc which has a pitch adsorption capacity of about35-45%. The decrease in pitch adsorption due to filtration was greaterfor the middle Georgia clay than for the east Georgia clay.

EXAMPLE 5

A leached Hydragloss® clay sample was obtained as filter cake from therotary vacuum filter and the filter cake reslurried at 25% solids anddivided into two samples. The first sample was treated with 20.0 lbs./tof Chlorhydrol® to produce a flowable slurry and spray dried. The secondsample was first dispersed with 0.15% of sodium hexametaphosphatedispersant (available commercially as Calgon Dispersant), and thentreated with 20 lbs./t of Chlorhydrol® before spray drying. The pitchadsorption characteristics of the two samples determined by the modifiedHughes method are given in Table IV.

                  TABLE IV                                                        ______________________________________                                        Treatment of Hydragloss ® Filter Cake with Chlorhydrol ®                     Calgon                        Pitch                                           Dispersant                                                                              Chlorhydrol ®   Adsorption                               Sample %         %            Slurry %                                        ______________________________________                                        1      --        1.0          fluid  82.5                                     2      .15%      1.0          thick  69.0                                     ______________________________________                                    

The results show that good pitch adsorption characteristics can beobtained by treating reslurried filter cake with sufficient Chlorhydrol®to obtain a good slurry flow or by treating dispersed filter cake slurrywith Chlorhydrol®.

EXAMPLE 6

A crude east Georgia Clay was obtained and dispersed at about 40% solidsusing sodium hexametaphosphate as the dispersant. Dispersant levels of2, 4, 6 and 8 lbs./t of clay were employed. The dispersed slurries weredegritted and solids reduced to 25%. Each slurry was then treated with20 lbs./t of active Chlorhydrol® and pan dried. Pitch adsorption for thefour samples, as determined by the modified Hughes method is given inTable V.

                  TABLE V                                                         ______________________________________                                        Effect of Dispersant on Pitch Adsorption of                                   Degritted East Georgia Clay                                                   Dispersant Level,                                                                          Slurry       Pitch Adsorption,                                   % Calgon     Consistency  %                                                   ______________________________________                                        .10          Moderately Fluid                                                                           82.5                                                .20          Moderately Thick                                                                           85.0                                                .30          Thick        82.5                                                .40          Very Thick   75.0                                                ______________________________________                                    

Very little difference in pitch absorption was observed for the foursamples, however, the lower level of dispersant would be preferred. Adifference in the consistency of the treated slurries was observed withthe sample containing the least amount of dispersant being the mostfluid and the sample containing the greatest amount of dispersant beingthe most viscous.

EXAMPLE 7

A coarse centrifuge underflow fraction from a middle Georgia clay havinga particle size of 30% minus 2 microns and a surface area of 8.5 m² /gmwas treated with from 8 to 21 lbs. Chlorhydrol® per ton of clay and thetreated slurries pan dried. The pitch adsorption characteristics of thetreated clays are given in Table VI.

Maximum pitch adsorption was obtained with 15 lbs./t of Chlorhydrol®,indicating that a suitable pitch adsorption product could be producedfrom a coarse underflow fraction.

EXAMPLE 8

Leached Hydraprint® filter cake, which is a delaminated clay producedfrom middle Georgia clays, was treated with Chlorhydrol® at 30% solidsand spray dried. The Hydraprint® fraction had a surface area of 11.3 m²/gm and a particle size of 72% minus 2 microns. Results of the test aregiven in Table VI.

                  TABLE VI                                                        ______________________________________                                        Pitch Adsorption of Treated Underflow Clay                                                 Chlorhydrol ®,                                                                        Pitch Adsorbed,                                      Clay         lbs./t      %                                                    ______________________________________                                        Centrifuge    8           9.0                                                 Underflow    12          17.5                                                 Underflow    15          70.0                                                 Underflow    18          67.5                                                 Underflow    21          10.0                                                 Hydraprint ®                                                                           15          62.5                                                 Hydraprint ®                                                                           18          74.0                                                 Hydraprint ®                                                                           21          75.0                                                 ______________________________________                                    

The results of the test indicated good pitch adsorption characteristicsat a treatment level of 18 to 21 lbs./t.

EXAMPLE 9

A degritted east Georgia clay slurry was treated with Chlorhydrol® atlevels ranging from 5 to 18 lbs./ton of clay. The treated slurries werepan dried and evaluated for pitch adsorption characteristics using themodified Hughes method. Results of the tests are given in Table VII.

                  TABLE VII                                                       ______________________________________                                        Pitch Adsorption of East Georgia Clay Treated                                 With Different Levels of Chlorhydrol ®                                    Chlorhydrol ®,                                                                           Pitch Adsorption,                                              lbs./t         %                                                              ______________________________________                                         5             10                                                             10             37.5                                                           12             74                                                             15             78                                                             18             75                                                             20             82.5                                                           ______________________________________                                    

The results indicate that good pitch adsorption characteristics can beobtained by treating degritted east Georgia clays with as little as 12lbs./t of Chlorhydrol® but that maximum adsorption is obtained with atleast 20 lbs. ton.

EXAMPLE 10

An undispersed middle Georgia Hydrasperse® fraction was treated with 18lbs./t of Chlorhydrol® and pan dried in an aluminum electric frying panas well as a teflon coated pan. The slurries were dried to about 5%moisture and then to dryness in an oven. The sample dried in theuncoated pan had a pitch adsorption value of 69% while the sample driedin the teflon coated pan had a value of 80%, indicating that theChlorhydrol® interacted with the aluminum during drying.

EXAMPLE 11

A fine particle, high surface area airfloated clay from South Carolinawas treated neat with Chlorhydrol® using a Vee Blendor. The treated clayproducts containing 0.75, 1.0 and 1.5% Chlorhydrol® were oven dried,milled and evaluated for their pitch adsorption capabilities using themodified Hughes method. The samples treated with 0.75, 1.0 and 1.5%Chlorhydrol® gave pitch adsorption values of 85, 24 and 20%respectively. The sample tested with 0.75% Chlorhydrol® had a pitchadsorption capacity of about twice that of talc.

EXAMPLE 12

The in situ formation of hydrotalcite in clay slurries was mostsuccessful for pitch control when utilizing undispersed starting clays.In this example a study was conducted of hydrotalcite formation in apredispersed Hydrafine® slurry prepared from production spray driedclay, as well as both dispersed and undispersed slurries prepared in thelaboratory from undried Hydrafine® filter cake. While productionHydrafine® and the dispersed Hydrafine® filter cake produced similarresults of 28.75 and 30% adsorption, respectively, the undispersedHydrafine® produced 42% adsorption levels. These results are shown inthe following Table VIII.

                  TABLE VIII                                                      ______________________________________                                        Hydrotalcite                                                                                     %       %    % Pitch                                       Clay    Al/Al + Mg Al.sub.2 O.sub.3                                                                      Mgo  Adsorbed                                      ______________________________________                                        Hydra-  .46        1.02    1.0  28.75  Production                             fine ®                                                                    Production                                                                    Hydra-  .44        1.02    1.0  30     Dispersed,                             fine ®                             treated                                Filter cake                                                                           .44        1.02    1.0  42     Undried,                                                                      undispersed                                    .44        1.02    1.0  42     Dried                                                                         undispersed                            ______________________________________                                    

EXAMPLE 13

A similar test with production Hydraprint® along with Hydraprint® filtercake collected from the plant was conducted. In this test, treatedHydraprint® from production exhibited a 35% adsorption capacity, whilethe dispersed filter cake yielded a 30% adsorption value. Undispersedtreated Hydraprint® filter cake provided 41% adsorption. These resultsare shown in the following Table IX.

                  TABLE IX                                                        ______________________________________                                        Hydrotalcite                                                                                     %       %    % Pitch                                       Clay    A/Al + Mg  Al.sub.2 O.sub.3                                                                      Mgo  Adsorbed                                      ______________________________________                                        Hydra-  .44        1.02    1.0  35     Production                             print ®                                                                   Production                                                                    Hydra-  .44        1.02    1.0  30     Dispersed,                             print ®                            treated                                Filter cake                                                                           .44        1.02    1.0  41     Dried,                                                                        undispersed                            ______________________________________                                    

EXAMPLE 14

The treatment of dispersed clays with hydrotalcite was found to be lesseffective than treatment of clays devoid of dispersants. It was foundthat the dispersion of previously treated clays rendered the onceeffective pitch control clay with essentially no adsorptive capacity.The Hydrasperse® filter cake treated with the hydrotalcite adsorbed47.5% of the pitch in test systems, but the addition of dispersantdestroyed the adsorptive capacity of the product. These results areshown in Table X, which is as follows:

                  TABLE X                                                         ______________________________________                                        Hydrotalcite                                                                                     %       %    % Pitch                                       Clay    Al/Al + Mg Al.sub.2 O.sub.3                                                                      Mgo  Adsorbed                                      ______________________________________                                        Hydra-  .44        1.02    1.0  47.5   Treated,                               sperse ®                           undispersed                            Filter cake                                                                           (control)               0                                             ______________________________________                                    

EXAMPLE 15

In order to evaluate the effectiveness of the Chlorhydrol® andhydrotalcite treatment, treatments with other compounds were carriedout. In these treatments, the Hydragloss 90® and Omnifil® clays weretreated with octyl, methyl, vinyl and monoamino silanes by dry mixture.The only silane treatment that yielded any adsorption was the octylsilane. On Hydrasperse® clay, the adsorption value is 20%, while onOmnifil® and Hydragloss 90® clays, the adsorption values were 17.5 and12%, respectively. These low values were not considered competitive inthe market.

EXAMPLE 16

Treatments with other compounds for comparison purposes are listed inTable XI. In this work a Hydrasperse® slurry was treated with thematerials listed in the Table. From the Table it will be noted that thetreatment of the Hydrasperse® with alum yielded 43.75% adsorption.However, alum was not considered as a candidate for treatment of theclay for pitch control because it is used as a pitch control agentalone, and in conjunction with other chemicals for pitch control in theabsence of clay.

In the other examples, kaolin clay was treated with zinc chloride andsodium hydroxide in quantities to form monohydroxy zinc, Zn(OH)⁺, forcation exchange bonding to the clay surface. The treatment yielded 45%pitch adsorption.

Most of the other materials reacted with the clay did not provide anypitch adsorption. The last three examples in Table XI involved treatmentof Omnifil® with 3 MeQMBHT and Araquad quaternary amines. Goodadsorption values were realized. However, these quaternary treatedproducts were very hydrophobic and were incompatible with water systems.Therefore, no further consideration was given to this method oftreatment. Table XI is as follows:

                  TABLE XI                                                        ______________________________________                                        Other Treatments                                                                                       % Pitch                                              Clay         Treatment Type                                                                            Adsorbed                                             ______________________________________                                        Hydrasperse ®                                                                          Alum        43.75                                                             Al-acetate  --                                                                ZnO         --                                                                Mg. Silicate                                                                              --                                                                ZnCl.sub.2  --                                                                Al.sub.2 O.sub.3                                                                          --                                                                Zn(OH).sup.+                                                                              45                                                                Mirapol A15 --                                                                NiSO.sub.4  --                                                                NiCl.sub.2  --                                                                U-care Polymer                                                                            --                                                                JR-125                                                                        JR-400      --                                                                MB2HT       46.25       quat                                                  Araquad 12-50                                                                             35          quat                                                  Al formate  16.75                                                ______________________________________                                    

EXAMPLE 17

Samples of Chlorhydrol®-treated clay and hydrotalcite-treated clays withexceptional pitch adsorption capabilities were submitted to the papertesting laboratory for evaluation in filler applications. The evaluationdemonstrated that the pitch control clays were acceptable in paperfiller applications. The specific results are set forth below. In thesestudies, the Chlorhydrol® treated clay was a degritted east Georgiacrude clay slurry (Area W) treated with 1.0 wt. % of Chlorhydrol®. Thehydrotalcite was a Hydrafine® clay, wherein the undispersed, undriedfilter cake was treated with hydrotalcite formed in situ using 1.02% Al₂O₃ and 1.0% MgO. These results are as follows:

                  TABLE XII                                                       ______________________________________                                        Evaluation of Optical Properties of Filled Paper Using                        Clays Modified for Pitch Control                                              ______________________________________                                        Handsheets were prepared from the following furnish:                          Pulp           70% Groundwood                                                                30% Bleached Softwood Kraft                                    Freeness       Kraft to 400 CSF, then blend                                                  with Groundwood                                                pH             Alum to pH 4.5                                                 Retention Aid  Betz 1260, 0.025% on furnish                                   Filler Loading 2.5, 5 and 10%                                                 Basis Weight   50 g/m (40#/ream)                                              ______________________________________                                        RESULTS:                                                                      RETENTION STUDY - No retention aid used                                                               RETENTION, %                                          ______________________________________                                        Area W control          46.9                                                  Area W Chlorhydrol ®                                                                              53.1                                                  Hydrafine ® Control 48.0                                                  Hydrafine ® Hydrotalcite                                                                          52.7                                                  Talc                    60.3                                                  ______________________________________                                                      Bright  White-  Opac- Pig- Re-                                                ness    ness    ity   ment tention                                            %       %       %     %    %                                    ______________________________________                                        Unfilled      64.0    43.5    95.3  --   --                                   2.5% Filler                                                                   Area W Control                                                                              63.5    42.5    96.0  2.56 73.1                                 Area W Chlorhydrol                                                                          63.6    42.8    95.9  2.79 79.6                                 Hydrafine Control                                                                           63.6    42.9    96.2  2.65 75.6                                 Hydrafine Hydrotalcite                                                                      62.9    41.7    95.9  2.56 73.1                                 Talc          63.3    42.8    95.9  2.24 74.8                                 5% Filler                                                                     Area W Control                                                                              63.9    42.2    96.2  5.19 79.8                                 Area W Chlorohydrol                                                                         64.1    43.2    96.1  4.96 82.7                                 Hydrafine Control                                                                           64.1    43.4    96.1  4.66 77.6                                 Hydrafine Hydrotalcite                                                                      63.8    42.7    96.4  4.72 78.7                                 Talc          63.5    43.2    95.8  4.54 75.7                                 10% Filler                                                                    Area W Control                                                                              64.6    44.5    96.3  9.89 82.4                                 Area W Chlorohydrol                                                                         64.7    44.6    96.4  9.51 82.7                                 Hydrafine Control                                                                           65.4    45.5    96.4  10.44                                                                              83.5                                 Hydrafine Hydrotalcite                                                                      65.3    45.5    96.8  10.35                                                                              86.2                                 Talc          64.4    44.2    95.9  9.62 64.1                                 ______________________________________                                    

EXAMPLE 18

In a production run, approximately 20 tons of dried pitch control claywere produced utilizing degritted Area W crude clay which had beentreated with 26 pounds of Chlorhydrol® per ton of clay. On evaluation asdescribed above, the pitch adsorption capacity of the resulting productwas found to be 74%, which illustrates that the invention can be carriedout on a large scale for commercial use.

The invention has been described herein with reference to certainpreferred embodiments. However, as obvious variations thereon willbecome apparent to those skilled in the art, the invention is not to beconsidered as limited thereto.

What is claimed is:
 1. Kaolin clay chemically modified to have improvedpitch adsorption by reaction with a double bond hydroxide of magnesiumand aluminum, said kaolin clay having been beneficiated prior to saidchemical modification.
 2. Kaolin clay chemically modified to haveimproved pitch adsorption according to claim 1, wherein said clay istreated with between 0.5 and 2.0 weight percent of said double bondhydroxide of magnesium and aluminum.
 3. Kaolin clay chemically modifiedto have improved pitch adsorption according to claim 1, wherein saidbeneficiated kaolin clay is selected from the group consisting ofdegritted clays, fraction clays, leached clays and mixtures thereof. 4.Kaolin clay chemically modified to have improved pitch adsorption byreaction with hydrotalcite, said hydrotalcite being formed in situ bythe reaction of aluminum chloride, magnesium chloride and sodiumhydroxide, said kaolin clay having been beneficiated prior to saidchemical modification.
 5. Kaolin clay chemically modified to haveimproved pitch adsorption according to claim 4, wherein said clay istreated with between 0.5 and 2.0 weight percent of said hydrotalcite. 6.Kaolin clay chemically modified to have improved pitch adsorptionaccording to claim 4, wherein said beneficiated kaolin clay is selectedfrom the group consisting of degritted clays, fraction clays, leachedclays and mixtures thereof.